Engine temperature running hotter than usual

[cdrusn]

I've always included a compression test of each cylinder. Not only should it show a difference (lower) compression in at least one but maybe two cylinders it will narrow your search.

[82DMC12]

I've always included a compression test of each cylinder. Not only should it show a difference (lower) compression in at least one but maybe two cylinders it will narrow your search.

Not a bad idea. I did a compression test last year just for the heck of it (I have a gauge) and all six cylinders were between 149 and 153 PSI so I have a good reference. I also rented a cooling system pump tester and I bought a combustion gas tester at Harbor freight so hopefully should have some answers and rule out a few things later today.

[82DMC12]

Well here is what I learned today.

1) Water pump belt is sufficiently tight
2) Bought a cooling system pressure tester pump and tested two caps - a new 15 PSI made in England cap from DMCMW, and a 16 PSI aftermarket cap from O'Reilly. Both tested OK.
3) Pumped up the cooling system to 15 PSI and it held pressure for 75 minutes without dropping at all. I have one tiny leak somewhere in the radiator, likely at an end cap joint because I can't see where the leak is unless I were to remove the shroud and possibly the fans. This is a repro radiator from DMCMW and is about 7 years old. I'll have to address this at a later day because radiators seem to be out of stock, however the tiny leak (a few drips after an hour) isn't enough to lose pressure.
4) Did combustion gas test in the SS overflow bottle. Waited until the thermostat opened, waited another 5 minutes, then used the tester. No sign of combustion gas in the test fluid. So, I think I can successfully rule out anything head gasket related.
5) Re-bled the radiator using the DPI radiator bleed kit. This time I pinched off the hose between the Tee and the metal pipe where the return flows to so that I was positive anything coming out of the bleeder was actually coming from the radiator and backed-up from the return pipe. Definitely well-bled now.
6) Went for a test drive with the same results. By the time I got home 15 to 20 minutes later, my temp was just below 220 with fans roaring (confirmed both are turning visually) and they are not taking the temp down, but the temp also isn't rising. It hasn't actually touched 220F during all this episode.
7) Once I got home with the car idling and temp nearly at 220F, I used an IR thermometer gun to check various spots between the thermostat and otterstat and confirmed the temp is around 197 to 215F at most.

It's been suggested that maybe my water pump is worn and not moving as much water as it should. I did have the water pump out of the car when I was in the valley this spring and of course inspected it and did not see anything inside or outside that looked worn but I guess it's hard to say. I do know that this problem suddenly started and hasn't been slowly creeping up like I would think progressive wear to the pump vanes would do.

It's my belief that the fans should be able to cool things down enough where they cycle on and off at idle (with A/C off). That's not happening. In fact when I first started the car in my garage and was bleeding, etc the temp was about 175F. It wasn't until I backed out and started driving that the temp started to climb, especially once I hit about 55 mph for a few minutes. Then the temp comes up to 215F and won't come back down even back at idle.

Any great ideas on what to check next?

[82DMC12]

I forgot to mention one thing. Not sure if this is relevant. But I had to have the radiator cap off of the expansion tank so that I could use the combustion gas tester. I started the car cold with the cap off and let the car idle until the thermostat clearly opened so that combustion gas, if there is any, is circulating back to the tank. I started the car with the tank half full. By the time the thermostat opened, within about 5 minutes, the level was coming up in the expansion tank until it actually started to overflow and spill out, so I quickly went and shut off the car, and it continued to overflow for a moment after I shut the car off.

I then drew about a quart out of the tank before restarting the car so I could use the tester without accidently sucking up coolant into it. The instructions for the tester say to warm the car up without the cap so that's what I did.

I get that the coolant will expand as it gets hot but is that normal? Should the expansion tank overflow like that with the cap off?

[DMC-Ron]

I forgot to mention one thing. Not sure if this is relevant. But I had to have the radiator cap off of the expansion tank so that I could use the combustion gas tester. I started the car cold with the cap off and let the car idle until the thermostat clearly opened so that combustion gas, if there is any, is circulating back to the tank. I started the car with the tank half full. By the time the thermostat opened, within about 5 minutes, the level was coming up in the expansion tank until it actually started to overflow and spill out, so I quickly went and shut off the car, and it continued to overflow for a moment after I shut the car off.

I then drew about a quart out of the tank before restarting the car so I could use the tester without accidently sucking up coolant into it. The instructions for the tester say to warm the car up without the cap so that's what I did.

I get that the coolant will expand as it gets hot but is that normal? Should the expansion tank overflow like that with the cap off?

That amount of change in the level of the reservoir tank you're reporting seems excessive. My reservoir level sits about an 1 1/4 inch down when cold and does not overflow when hot. Liquid coolant obviously expands with heat but overflowing a tank that's only half full when cold is a lot of expansion. I would have suggested that you need to bleed your water pump but you mentioned that you have Toby's auto-bleed so that should be automatic. The DPNW self bleeder kit usually has a valve that can disable the auto-bleed. Has that been inadvertently closed?

Ron

[82DMC12]

That amount of change in the level of the reservoir tank you're reporting seems excessive. My reservoir level sits about an 1 1/4 inch down when cold and does not overflow when hot. Liquid coolant obviously expands with heat but overflowing a tank that's only half full when cold is a lot of expansion. I would have suggested that you need to bleed your water pump but you mentioned that you have Toby's auto-bleed so that should be automatic. The DPNW self bleeder kit usually has a valve that can disable the auto-bleed. Has that been inadvertently closed?

Ron

I have an older version of the Toby kit that doesn't have a ball valve so it's always bleeding off a portion to the overflow tank.

Maybe I'll order a new thermostat and gasket as well as do another look at the bleeder kit. Maybe something has obstructed the bleed screw inside the thermostat housing. Might be smart to get the new kit with the ball valve anyway.

Sent from my Pixel 3a using Tapatalk

[David T]

On a car that has a good, tight, leakproof system, once it is properly bled, you should not need an "auto bleeder kit". If you keep getting air you either have a leak or a bad head gasket and that should be fixed.

[Helirich]

That amount of change in the level of the reservoir tank you're reporting seems excessive. My reservoir level sits about an 1 1/4 inch down when cold and does not overflow when hot. Liquid coolant obviously expands with heat but overflowing a tank that's only half full when cold is a lot of expansion.

Ron

That is an interesting observation. I might have to try this test. This is the only car I have that has a reservoir tank, but every other car will overflow if the cap is removed and warmed up. Can’t say I’ve ever measured how much. If water is boiling some where, I don’t think it would stop.

As far as the OPs issue, I lean to the water pump not pumping good. Maybe a good flush?

[FLUX @88]

Possible cogged heater core or radiator? I also recommend purchasing a coolant vacuum filler. Yes you can fill and bleed the car normally but I have had great success using a vacuum filler to eliminate any air in the system.

[David T]

A vacuum filler makes filling faster and does not require as much bleeding but you will still have to do some bleeding of air. The major benefit to using a vacuum filler is that you can get all of the coolant in without having to wait for the thermostat to open by warming up the motor. Always check that the thermostat has a jiggle pin or at least a tiny (1/16") hole to allow air to pass. Another tip, the gasket fits AROUND the thermostat, the edge of the thermostat fits into the groove of the gasket.